Landfilling of organic material leads to CH4 emissions, which result in greenhouse gas potential 21 times higher than that of CO2 (European Cooperation in the field of Scientific and Technical Research 2002).

During the combustion of particleboard it is important to have the appropriate conditions; otherwise incomplete combustion can result in the formation of toxic compounds (Risholm-Sundman and Vestin 2005).

The alternatives to incineration or the disposal of wood waste in landfills constitute low-profit solutions that can also be hostile to the environment (Michanickl 1996). On the other hand, recycling causes less harm to the environment.

From an environmental point of view, the increased recycling of recovered wood increases the total volume of CO2 stored as wood-based products, enlarging the life-cycle of the fixed carbon in the new recycled products. However, a negative effect is that waste wood currently contains physical and chemical contaminants (metals, stones, glues, paints, melamines etc.), that have an important influence on the product quality and this constitutes an obstacle preventing 100% utilisation of recovered wood for use as a raw material for another product.

The current strategies in managing wood waste and their impact on the environment are shown in Table 2 (European Commission, 1997).

A statistic analysis indicates that approximately 1.5 billion tyres are discarded every year worldwide and from these 250 millions in Europe (Jiang 2003). The ever-increasing environmental hazard from the waste tyres has emerged. Whilst tyre usage is increasing, the markets for reusable car tyres from re-treading appear to be declining. There are a number of options for dealing with waste tyres but these do not appear to be sufficiently cost effective to drive the market for recovery.

Tyre design for single-use is a contributing factor, tyres are designed to last and are therefore difficult to break down and separate into their constituent parts. Adding to this problem, disposal releases potentially harmful compounds into the environment, e.g. polyaromatic hydrocarbons (PAHs), benzene and phenol which have suspected carcinogenic properties.

Landfill disposal and incineration also release these harmful substances:

Most countries have relied on landfilling to dispose of tyres but the limited space and the potential for reuse has led to many countries imposing a ban on this practice. Legislation to control waste disposal is tightening with the requirement to divert waste from landfill. Tyres, in particular, represent a very difficult disposal problem if landfill is not an option when the Landfill Directive is implemented. Landfill is not a long term solution because of their saturation and of environmental laws.

On the other hand, burning tyres can have a serious environmental impact. They produce vast quantities of harmful emissions that will pollute the atmosphere and water courses through run-off and the high energy content of tyres means they can burn for long periods.

Moreover, the cost of used tyre treatment is reaching a high level almost everywhere. If nothing was done, the number of uncontrolled and illegal landfills/stockpiles would grow as would the accompanying pollution risks. Without adequate alternatives current trends in the fly-tipping of tyres will worsen, increasing the problems faced by local authorities. Limited resources already present serious difficulties when dealing with scrap tyres.

In order to solve this problem, two ways of recycling can be considered:

• Incineration with energy recovery, with taking into account the environmental constraints.

• Shredding in order to recover rubber and steel.

Although some local programs for recycling have been started around Europe very few are generalized at a country or even a regional level.

It is quite clear that the problem caused by used tyres is linked to the difficulty to identify who has the responsibility for the waste and who should pay for disposal. Manufacturers, distributors, or consumers? One thing is sure, solutions have to be found. Not only should this huge environmental problem be solved but the solutions need to be economical.